It has previously been known that electrical pulses can be used to provide antimicrobial treatment for food products. Some of the prior food treatment systems include a flow-through processor. The processors contained first and second electrodes which were charged to high voltages. The high voltage electrodes create high electrical field strengths across a space extending between the electrodes. Field strengths of 5-100 kilovolts per centimeter have been reported.
The processes of the prior art are indicated for use in applying pulsed electric fields to juices, liquid egg products, and other types of pumpable foods. In such systems the electrical treatment is combined with a heat treatment to improve microbial inactivation. This approach in essence combines heat pasteurization with electrical pulse treatment to inactivate microbial populations. However, the use of heat processing necessarily has significant and sometimes derogatory effects upon the taste, color, and other properties of the resultant food products. Thus there is a need for improved processes which do not require combined elevated heat treatment and electrical pulse treatment to accomplish suitable inactivation of microbes.
Prior art electrical pulse treatment systems have also been flawed in having processing chamber designs and methods which result in accumulations of materials such as organic molecules upon the electrodes. Such accumulations can cause fouling of the processor flow channels. More typically, the fouling will affect the properties of the electrical field emanating from the electrodes and their interaction with the fluid being processed. This can lead to non-uniform pulse distribution into the flowing product, which in turn can result in inadequate microbial inactivation. Fouling of processor electrodes can also result in increasing heat buildup at the electrodes. This heat buildup further exacerbates the fouling of the electrodes.
Prior art systems have also been deficient in utilizing exponentially decaying wave forms in the generated electrical pulses supplied to the electrodes. Such exponentially decaying pulse shapes fail to fully utilize the energy being supplied in a manner which is effective at inactivating the microbes. The prior art systems further have generally used pulse generators which are relatively expensive to build and operate. This has been a drawback to adoption of electrical pulse treatment of food products.
Electrical pulse treatment of food is further complicated when the food products being treated are not homogeneous liquids but instead suspensions or mixtures of liquids with entrained solid particles. The added difficulty of processing such particulate foods has challenged the previously known electrical pulse food processing techniques. The exact causes and mechanisms which reduce the effectiveness of prior electrical pulse food treatment systems may not be known. However, it is believed that the increased difficulty may be due to one or more of the following considerations.
One problem which is of increased difficulty when processing particulate foods is the risk of dielectric variations and dielectric breakdowns which can occur between the electrodes within the food being processed. The risk of such dielectric variations and breakdowns are increased substantially due to localized electrical path tracking along the surfaces of particles contained in the particulate foods. The variety of food particles, variations in food particle sizes and variations in the makeup of the suspending liquids severely increase the difficulty in solving this problem. Dielectric variations and dielectric breakdowns can restrict the electrical pulse voltages and currents which can be applied and developed during electrical pulse treatment. This can further limit the effectiveness of the process and lead to increased processing steps, increased processing time, or increased processing energy being needed in an effort to successfully inactivate microbes or enzymes contained in the foods being treated.
Particulate foods have also been additionally challenging in that prior electrical pulse treatment chambers have demonstrated relatively stronger electrical field strengths at or near the surfaces of the electrodes. This increased electrical field strength at the electrodes exacerbates the problem explained immediately above. It also can lead to electrolysis of food particles and other components of the food product being processed. Food components which experience electrolysis undergo changes which in effect transform the electrolysis products into contaminants which degrade the quality of the resultant food product.
Particulate foods can also pose added difficulty in electrode fouling. The fouling can occur from electrolysis of food particles or other components of the food. Fouling can also occur due to other reasons, such as heat buildup at the electrodes or other physical or chemical changes which can occur in the food product being processed.
Thus there remains a need for improved electrical pulse food treatment systems for treating flowable food products. Further there is a need for improved electrical pulse food treatment systems which have improved efficacy in treating flowable food products which include suspended or otherwise mixed food particles within a liquid carrier.